208 – Diffraction of Light

Diffraction at the single slit 

Introduction to:  

• Diffraction  
• Monochromatic light  

Material:

• Laser pointer   
• Laser safety goggles  
• Sharp Knife  
• Fastening material (clothespins / paper clips / adhesive tape)  
• Strong paper (e.g. construction paper, approx. 7 cm x 20 cm, approx. 130-200 g/m²)  
• Ruler   
• Support for laser (possibly height-adjustable)  
• Cutting surface (hard, stable)  
• Sheet of white paper  

Instructions:   

• Cut a straight slit in the construction paper with the help of the knife and ruler.   
• The width of the gap should be about 0.1 mm.  
• Attach the paper to the ruler with the fastening material and place it at a distance of about 2 m from a wall.  
• Set up the laser in such a way that the laser beam hits the gap in the construction paper straight at a distance of about 15 cm.  
• Always use the safety goggles.  
• Attach the sheet of paper as a screen to the point where the light beam hits the wall.  
• Darken the room.

Observation:  

• The light spot on the screen is not point-shaped, but elongated in the direction perpendicular to the slit.  

Explication: 

• The light is diffracted at the edges of the gap.  

Tips: 

• Move the laser beam back and forth slightly with the contact surface to set an optimal result.